ANDRONIKI MILTIADOU-FEZANS, a structural engineer specializing in historic structures, is director of the Directorate Special for the Promotion and Enhancement of Cultural Heritage and Contemporary Creation at the Ministry of Culture, Education, and Religious Affairs of the Hellenic Republic. She has been responsible for many structural restoration projects in Greece and teaches at the Raymond Lemaire International Centre for Conservation in Belgium and at the postgraduate conservation program of the National Technical University of Athens.

CLAUDIO MODENA is a professor of structural engineering at the University of Padua. He has served on a number of research and scientific committees related to earthquake engineering and seismic risk and has done extensive consulting internationally, focusing generally on the conservation of historic masonry structures.

JOHN OCHSENDORF is a structural engineer specializing in the analysis and design of masonry structures and is a professor at the Massachusetts Institute of Technology, holding a joint appointment in the departments of Architecture and Civil and Environmental Engineering. He is a founding partner of Ochsendorf DeJong and Block Engineering.

They spoke with CLAUDIA CANCINO, a senior project specialist at the Getty Conservation Institute, and JEFFREY LEVIN, editor of Conservation Perspectives, The GCI Newsletter.

CLAUDIA CANCINO In recent decades, structural interventions on historic structures, appropriate or not, have sparked a series of discussions about the role an engineer should play in a conservation project. What do you think is the role of a preservation engineer?

ANDRONIKI MILTIADOU-FEZANS Structural intervention on historic structures is a matter that cannot be dealt with only by a structural engineer—it is a project for a multidisciplinary team. Of course within the team, an engineer plays a very important role. His or her main duty is to document a structure’s bearing system, to design and supervise the necessary investigations, to assess the structure in its current state, and to design the necessary interventions in collaboration with architects, archaeologists, and others—all in order to ensure as much as possible the survival of the structure from damage or even collapse. Of course, the engineer has the responsibility of ensuring that human life is protected, but at the same time, together with safety, has to propose interventions that take into account all the other values—such as historical, architectural, and aesthetic—in an effort to limit their possible alterations due to intervention. He or she needs to elaborate on alternative solutions and to put them on the table to be debated with other professionals on the team to reach an optimum solution. Consequently, the engineer should have the ability to communicate these structural matters to the team, so the team can discuss them and reach the optimum compromise.

CLAUDIO MODENAI agree that the role of the engineer is to consult with the team and to bring to the team his knowledge about the structural performance of different types of material and the ways to evaluate them.

JOHN OCHSENDORFFor me, the first responsibility of an engineer is to work closely with the other disciplines—historians to learn the history of a monument, architects to learn the design intent for future use, conservators to understand the challenges in terms of material conservation, and also the property owner to understand the owner’s needs and challenges. Engineers must then offer a range of solutions that can be debated on their merits. Engineering problems never have just one solution. Furthermore, every solution has pros and cons in terms of cost, authenticity, durability, and reversibility. The primary role of the preservation engineer is to put on the table a range of solutions. In many cases, doing nothing should be on the table. Too often, it is not.

CANCINOI also agree that engineers should be part of a team in a conservation project, but I was wondering about their capabilities to intervene in historic structures. Do engineers in general, or structural engineers, have the knowledge to understand a historic building—to study and to analyze the load forces, and to understand how the building has performed over time?

MODENAI believe that engineers in these cases are aware that they have to work together with other disciplines. But the issue is the capability to do it in an appropriate way. The way of dealing with historic structures is quite different from the way of handling the same problems in recent construction. Engineers are trained to deal with newer projects. In Italy now we have some courses dealing with the problems of historic structures, and the situation is improving, but the main training engineers receive at the universities relates to new construction.

Photo: Courtesy of Androniki Miltiadou-Fezans
In most universities, engineers primarily study new concrete and steel structures, and less often masonry and wood structures. So even good and experienced engineers need additional education and training to deal with historic structures.

MILTIADOU-FEZANSIn most universities, engineers primarily study new concrete and steel structures, and less often masonry and wood structures. So even good and experienced engineers need additional education and training to deal with historic structures. But also young engineers lack training in historic structures, so postgraduate courses and additional job training are very important.

OCHSENDORFI agree—but I would like to emphasize that if an engineer on a team does not take a holistic and thoughtful approach in proposing multiple solutions or a range of alternatives, then it’s the responsibility of the client and the rest of the team to say, “We have the wrong engineer.” I’ve often seen an engineer come in with a report that gives one answer—one intervention—and then the client and the rest of the team says, “Ah, the engineer has spoken. Now we must add steel.” But it would be better to say, “We need a second opinion.” If someone said the Mona Lisa was in danger of decay and needed to be dipped in epoxy to be secured for future generations, there would be a second opinion! I can give you examples of some of the greatest monuments on the planet where the word of a single engineer with a single intervention was taken without question.

MODENAThis is the problem of having the authorities decide on projects. In Italy, the general secretariat of the Italian Ministry of Cultural Heritage is well aware of this and is producing guidelines for the officials who work in the offices that have to examine these projects. Training those who have to make decisions is a very important and very real issue. This work is very challenging for decision makers, who are often architects. So there is also the problem of training the architects to evaluate the work of the engineers.

MILTIADOU-FEZANSI think that at least in the countries with high seismicity, there has been an evolution in recent decades. A detailed study of proposed structural interventions by a team including at least an architect and an engineer is requested. Moreover, in Greece the final decision on approval for design projects is based on the recommendation of competent multidisciplinary scientific councils set up in compliance with national legislation. This procedure is very important with regard to both the protection of the monument and the burden of responsibility, because—at least in Greece—the structural engineers have a legal responsibility in the case of future damage and may not undertake alone the decision of reducing the severity of the design criteria in the case of monuments. In order to find an optimum intervention scheme that will both protect lives and preserve as much as possible the values of the monument, the seismic redesign action may depend upon acceptable damage levels, varying according to the use of the historic structure and, of course, its importance. Designing interventions for a classical monument like the Parthenon is completely different than for a building in use in a historic center. To this end, a certain categorization of various historic structures, based on their importance and occupancy, would play an essential role in the design of optimum interventions.

CANCINOSo there clearly is a need—and there has been for a while—to train engineers on structural interventions for historical constructions. However, it seems to be difficult to include the topic of historic structures within existing engineering curricula. Why is it a challenge for engineers to study, analyze, and propose interventions to historic buildings?

OCHSENDORFLet’s talk about the education of a typical engineer. I teach in the United States, but I’ve worked in universities in England, Spain, Italy, and Australia, so I have a reasonable understanding of engineering education internationally. First of all, engineering education contains no history. It’s almost always the case that there are no courses related to the history of construction or the history of engineering. Second, in the typical engineering education, students are given problem after problem for four to six years, and the problems almost always have one answer. We can all point to exemplary cases of engineering education where there is more open-ended thinking, but in our typical education we are taught that there is only one answer. Engineers could do a calculation on a standing arch, and their calculation may say that the arch should not be standing. I tell students that if their calculation says the structure is not standing—and it is—then it’s not the structure that’s wrong. It’s their calculation. Third, students are taught that there are two materials—steel and reinforced concrete. There is an obsession with these two materials and with new construction. Very often, especially in some economies around the world, most of the work deals with existing buildings, not new buildings. And so that is a major handicap. It’s also true of architecture schools, but it’s even more true of engineering schools.

CANCINOI frequently come across papers that talk about the problem of engineers facing the unknown when they deal with historic buildings. That is probably because there is no training in materials other than modern ones.

MILTIADOU-FEZANSIt is true that a formally trained engineer will have lacunae in his education regarding the difficult problems of historical monuments. These are old structures, usually made from various types of masonry, constructed in different phases, suffering from new and old damage, and repaired or transformed over the past. There is a lack of sufficient understanding regarding their structural behavior, before and after interventions, related to uncertainties in the estimation of resistances and actions, as well as in the methods of analysis and verification. For example, interventions of fifty years ago—which were probably considered the best ones—used a lot of reinforced concrete, but earthquakes that happened later have proven that this approach was very invasive and not adequate. So the problems are quite complex.

MODENAI would say from a conceptual point of view, approaches to the problem of safety of historical monuments are present in some official normative documents. They say, for example, that structural models normally provide solutions that are on the safe side, but these solutions that normally we accept, we cannot accept in the case of existing historical structures. We say, for example, that you should not rely on only one model. We are saying that models can be used for performing sensibility checks, and so we have to check the imprints of some parameters. We teach that when intervening you should try to minimize changes in the structural response—otherwise the models will say nothing sensible. So the job of the engineer in the case of historical structures is much more complex and difficult than when designing a new project. Conceptually, all that is already clear. The real problem is how to put into practice such very general indications. In Italy, substantial efforts are being made to fill the gaps with courses taught for engineers and general architects on the history of architecture and on the structural problems of historic structures—such as the one I am teaching at the University of Padua.

CANCINODo formally trained engineers today at least have the capacity to adapt the knowledge provided to them to appropriately intervene in historic buildings?

MODENAIn my experience, structural engineers are trained for designing new structures, and not for dealing with problems of existing historical structures. In Italy, the so-called engineer-architects do much better. They are less prepared to deal with the most sophisticated structural models but better prepared to deal with holistic approaches to structural safety of historical constructions.

JEFFREY LEVINShould more attention be paid to traditional or historic repair techniques that have, in fact, at least sustained these structures over time?

MODENAThis is a big debate. The problem is the appropriate use of traditional knowledge. But I am absolutely convinced that when we intervene and substantially change the structural behavior, we are not able to control what the behavior will be in the future. But I would also comment at this point on a paper I recently wrote proposing that instead of talking about compatibility or reversibility, it is much more appropriate to speak in terms of reparability. Historic buildings have suffered damage and were repaired. The problem now is when we intervene using modern technologies. I am very much concerned about the use of “innovative solutions.” Some novel solutions do not always perform well, and in any case they make things much more difficult to repair. We should be guided by experience, and focus much more on a real understanding of the design and on selecting appropriate materials, no matter if they are traditional or innovative.

MILTIADOU-FEZANSI agree that reversibility and re-interventionality—as we say in the relevant Greek draft regulatory document for seismic protection of monuments—are basic performance requirements for structural interventions. When reversibility cannot be ensured, we must try to give future generations the possibility to intervene again. I also totally agree that models cannot be the only guiding factor for our decisions. Models are just one tool. They should be calibrated on the basis of the evidence existing in the monument as such, adequately investigated and assessed by the expert team. In old structures, there are a lot of secrets, and we must spend time in situ to understand and evaluate what has happened in the past in order to make a proposal for the future.

OCHSENDORFI do not believe that we understand the seismic performance of historic buildings very well at all. That includes university researchers—but even more so practitioners. I think we are in our infancy. If you ask how a complex structure like the Basilica of St. Francis of Assisi behaves, I don’t think we understand it well—even if we remove the seismic issue and talk only about durability of materials. Of course structures are maintained over the centuries. The great cathedrals of Europe had large maintenance campaigns about every hundred years. But many of our solutions have shortened those maintenance intervals in recent years, primarily because we have had too much confidence in new materials. If you look at the history of preservation engineering, it’s one idea after another that was shortly discredited. So I think we need to be skeptical of new materials. The interventions of the nineteenth century were often better than the interventions of the twentieth century.

Photo: Courtesy of Claudio Modena
We should be guided by experience, and focus much more on a real understanding of the design and on selecting appropriate materials, no matter if they are traditional or innovative.

CANCINOWould it be useful for engineers and architects to have training in interventions that failed—the process of how the interventions were designed and implemented and the impact that those interventions had on historic buildings? At least we could learn from mistakes in the field.

MILTIADOU-FEZANSIn my postgraduate courses, I always start with the failures of the past. These are vital guides for the present. It is also very educative if one has the opportunity to see some historic structures after an earthquake—to directly and personally observe the eventual problems caused by past interventions. For instance, when I visited Kalamata in South Peloponnese after the 1986 earthquake, I was shocked by the fallen cupolas, framed in concrete, that were lying in the interiors of the churches.

MODENAI agree that it is better to avoid using materials of which we know little regarding their interaction with original existing material. But we also have the problem of preserving historic centers where people live. There are hundreds of thousands of historic buildings where people live and make changes. In these cases, the problem is even more complex. Those buildings are different than empty monuments. And this is a big issue in Italy, where the owners, the architects, and the contractors are not aware of the problems.

CANCINOEven when you have an adequate team, with an architect and structural engineer, and you offer multiple solutions to city building officials, these officials can have problems accepting minimal interventions or nonstructural solutions. Why do you think that’s the case?

MODENAIn Italy in the case of historic buildings, it is almost compulsory to improve safety, but it is not necessary to demonstrate the same level of safety with historic buildings as it is with newer buildings. In our codes, in the case of existing structures, there are three possible ways to intervene. First, by retrofitting. This means to formally demonstrate that the safety of the existing structure after intervention is the same as it would be for a new building constructed in the same place with the same designation. But it is also considered a possibility—almost an obligation in the case of historic constructions—to intervene by “only” improving the safety, demonstrating that the safety after the intervention is better than the safety was before. This is actually the main normative support to the design approach of “minimum interventions.” And it is also possible to intervene without demonstrating that the intervention that is proposed will improve the “global safety” of the structure, but rather simply repair a local damage or prevent possible failures. This is written into our code in Italy. So we accept the idea that with regard to existing structures, we have to form an approach that is different from the one we use for new construction. I must say, however, that the debate on such issues was still heated, even in the committee (of which I am a member) that recently updated our national structural code.

MILTIADOU-FEZANSIn my country, within the Earthquake Planning and Protection Organization, we are now working on the preparation of a code for structural interventions on existing masonry buildings. It has not been finalized yet, but certainly the aforementioned approach of “safety improvement” is also under consideration. The problem is that the criteria to judge the level of “an improvement” are not so clear, owing to lack of knowledge regarding the behavior of historic masonry structures at an international level. Existing masonry buildings—not historic ones—that are not engineered have the same problems, because they are inhabited and because there is danger during an earthquake. Thus, one has to find a solution, at least for the time being, based on the knowledge available today. One cannot wait for the necessary research work to be completed to elaborate a code. We are trying to quantify existing knowledge and to produce code documents to be applied to existing masonry structures, because we must never forget that while thousands of historic masonry structures have survived, many have been damaged, and many others have collapsed.

OCHSENDORFI think codes are a major problem. Italy is doing very good work and is among the best in the world in trying to make the codes relevant to historic structures. Claudio is a major leader in that. Here in the United States, it’s possible for engineers to use their judgment and to make exemptions, but that does not happen enough. I think we rely too much on codes that are inappropriate. Returning to your question about the building officials, Claudia, I think the desire to intervene is natural. With older structures, people think we must do something. There’s a lot of cultural pressure to make an intervention because we believe in a progressive world in which the technology we have today is better than what we had a hundred years ago—which is true in neuroscience and in many other fields. I also think that building officials have an expectation to intervene, which is not so healthy sometimes.

LEVINWhat can be done in the United States to further the kind of approach that Italy has taken? What steps would you suggest to change the way that we look at historic buildings in the context of the codes?

OCHSENDORFIt’s a long process. Codes take a long time to change. I think what can help are case studies that can provide examples of interventions that are appropriate or inappropriate—as well as instituting certification programs for engineers to work in preservation. This is something that the United Kingdom has recently pioneered, and I think this it is applicable in many countries where engineers work on historic structures.

MODENAMaster courses for graduate students and special training courses for engineers after graduation can certainly help.

MILTIADOU-FEZANSIt is not only the engineers who need training, but contractors as well. Because while the project ideas and the drawings may be good, the personnel implementing the interventions—the workers, the technicians, and the contractors—should also be experienced and effective to achieve improvement of structural behavior. So all need to be trained and to be able to provide certifications that ensure their capability to undertake the work. Interventions must be carefully applied, because if they are not applied correctly they can be very invasive and even dangerous.

MODENAOne of the most important advances in the technology field is in the tools used to conduct analyses that help us better understand a structure and its materials. By using a combination of nondestructive and minimally destructive monitoring in the case of important monuments, we have the technological tools to make investigations and appropriate user models, and to combine experimental and numerical models. These advances can be very useful in designing minimal interventions.

OCHSENDORFI agree completely, but I will also say that oftentimes we don’t have the patience to wait. For example, if there’s a crack in a monument that is worrying people—and it’s been there for two hundred years—I would say, “Well, let’s monitor for five years, and then we can talk.” Often the timeline is so short. People want to spend the money and do a project in six months. We need to have more patience.

MODENAAbsolutely. In the big projects, it is much better to have more time. We have to consider that some of these monuments took decades or even centuries to be built. So we cannot intervene as we would with new construction. We need time to deal appropriately with their problems.

MILTIADOU-FEZANSIn our guidelines, we have included this concept of incremental progress in design and in the implementation of interventions. This means that one can undertake a first step of limited interventions, and then monitor the behavior of the structure and continue with another set of interventions, if necessary. Needless to say, in parallel with the first series of interventions, various hidden elements of the monument may be investigated, while real information on the dynamic response of the structure, through a monitoring system, may serve to calibrate future models for the design of the next phase of interventions. This was the case of the katholikon of Daphni Monastery in Attica, Greece, a World Heritage Monument.

CANCINOWe have touched a lot on the topic of capacity-building of engineers and officials, and what I’d like to ask now is what you all think needs to be done to improve the training of preservation engineers.

Photo: Courtesy of the John D. and
Catherine T. MacArthur Foundation
Engineering problems never have just one solution. Furthermore, every solution has pros and cons in terms of cost, authenticity, durability, and reversibility. The primary role of the preservation engineer is to put on the table a range of solutions.

MILTIADOU-FEZANSI think that the improvement of education and training should go in the following directions. First, in technical universities the mechanics of masonry and timber structures should be taught systematically, together with an advanced technology course on materials. Second, institutionalized continuous education should be permanently organized for the training of the professionals who have completed their university education but have no time or means to go on to postgraduate programs. For example, in Greece we have a state institution that organizes training courses for engineers and other state officials responsible for the design and application of a project or the approval of project designs. Third, master courses should be further enhanced. In these master courses, it is vital to give the various professionals who work together—engineers, architects, art historians, and so forth—the opportunity to gain an understanding of their mutual interests and knowledge, and of the need to work together.

MODENACertainly special training is needed for structural engineers who deal with preservation problems. In Padua at my university we have a course for engineers/architects, but we recently decided to start a new engineering course that is more concerned with existing structures—and historic structures in particular. This certainly is a need that is not presently being addressed in courses for structural engineers. As I said before, structural engineers are very well trained to design new structures but they don’t know anything about history and traditional solutions. So in Italy we are trying to develop these courses for people who will work on historic structures.

OCHSENDORFI want to make a very central point, which is related to education. There are really three big reasons why an engineer might intervene or be pushed to intervene in a historic structure. The first is fear and liability. If a building collapses, the engineer is responsible, and that can motivate interventions. The second motivator is financial reward. Often the engineer’s fee is a portion of the overall contract, and engineers have offices that they’re trying to support—and so that is a motivator to do a bigger intervention. And the third motivator is a lack of knowledge—such as in the behavior of a brick vault or in the behavior of a timber truss. Education can address the lack of knowledge, and we can do that through case studies, training programs, and certification programs, which I think should be a postgraduate degree in preservation engineering. Still, those other issues remain—the fear and liability, and the financial motivation. So training is important, but it will only solve one part of what drives the interventions in historic monuments.

MILTIADOU-FEZANSTraining and postgraduate studies for engineers can also have an impact on the financial issue. If more engineers are educated in a better way to understand the structural behavior of historic structures, then they will avoid possible invasive interventions that might be dangerous or not useful. And this will happen because if they are aware of the danger, they will not sign off on inappropriate interventions for which they are responsible in case of failure. So I think that the training and education of engineers can have a broad impact.